Friday 10 July 2015

Charging Current Indicator Circuit for Batteries

Within this post we find out about a basic battery current sensor with indicator circuit which allows the amount of current used by the battery while charging or by any other load and displays it by means of discrete LEDs.

Generally most battery charging indicators use the voltage level of the battery to reveal its charging condition, here rather than voltage the current (amps) magnitude is utilized for measuring the charging position.
Utilizing current as the measuring parameter allows a more precise assessment of the battery charging position. The circuit can be effective at showing the immediate health of a attached battery by translating its current acquiring ability while its being charged.
Talking about the demonstrated circuit, we are able to notice four opamps configured as comparators in which each opamp possesses it own presetable current sensing inputs.
A high watt resistor Rx forms the current to voltage converter component which sustains the used current by the battery or the load and results it into a related voltage level and gives it to the opamp inputs.
P1 upto P4 are adjusted such that the A1 to A4 opamp non-inverting inputs turn out to be above their specific inverting inputs as a reaction to the reducing current consumption by the battery as it gets to it full charge status.
For example P1 might be adjusted such that A1 pin3 turns into somewhat more than its pin2 when the battery uses the highest amount of current (a known specified level), which is when its fully discharged.
P2 might be adjusted exactly the same when the battery gets charged to certain somewhat higher voltage level and its current utilization is decreased correspondingly.
Likewise P3 and P4 might be adjusted for the next lower voltage levels across Rx due to the battery's increased charge level until it's fully charged.
These types of numerous current consumption levels from maximum to minimum is mentioned by the related LEDs linked across the outputs of A1 to A4 in a sequential manner, whereby only a single LED lights up at any specific presented example for showing the appropriate battery current levels.


Parts List for the offered battery current indicator circuit
R1----R5 = 1k
P1-----P4 = 1k presets
A1-----A4 = LM324 IC
Diode = 1N4007 or 1N4148
Rx = 0.6/specified battery charging current
The right way to establish the circuit
At first maintain all the preset slider arms in the direction of the ground end.
Disconnect the P1---P4 connection with Rx and connect it with an external variable voltage source which may be simply made with a 1K pot.
For producing the variable power supply, take a 1K or a 10K pot, connect its outer terminals with the supply rails and connect its center terminal with the free end of P1---P4 which was turned off from Rx.
Adjust the pot and create a 0.7V at the center lead of the pot.
Now adjust the P1 such that the white LEd just brightens.
Increase the pot center lead voltage to 1V and set P2 such that the yellow LED just brightens, shutting off the red LED.
Next, increase the pot center lead voltage to 1.3V and consequently to 1.5V and adjust P3 and P4 exactly the same as done for P1, P2.
As soon as the setting is finished the pot could be taken off and the P1----P4 end reconnected to the Rx point.
The above range of 0.6V to 1.5V will probably be subject to the chosen Rx value along with the preferred current range, where 1.5V might be deemed to the maximum voltage across Rx produced for the exact maximum preferred charging current for the battery or some other load.
For instance, a 1 ohm resistor chosen for Rx will produce 1.5 V across it when a current of 1.5 amp is passed via it, whereas the same voltage is going to be produced for a 5 amp current if Rx is chosen as 0.3 ohms etc.
The formula for choosing Rx = 1.5/maximum charging current.


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